Pressure responsive device



Oct. 18, 1949. s. CRUM 2,485,433

PRESSURE RESPONSIVE DEVICE Filed April 4, 1846 3 Sheets-Sheet l INVENTOR. JTEFHEN CHI/M Oct. 18, 1949. s. cRuM 2,485,433

PRESSURE RESPONSIVE DEVICE 3 Sheets-Sheet 2 Filed April 4, 1946 INVENTOR. fiTfPHEN C/YUM Oct. 18, 1949. 5, CRUM 2,485,433

PRES SURE RESPONSIVE DEV ICE Filed April 4, 1946 3 Sheets-Sheet 3 fi J.

ELECI N HND Patented Oct. 18 1949 PRESSURE RESPONSIYE DEVICE Stephen Crum, Minneapolis,.Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application April 4, 1946, Serial No. 659,653

14 Claims. 1

The present invention relates to pressure responsive devices and more particularly to a manifold pressure control for internal combustion aircraft engines.

In my co-pending application entitled Engine power control apparatus, Serial No. 659,651, filed on even date herewith, is disclosed apparatus for coordinating engine speed and intake manifold pressure to obtain desired operating conditions for the various power requirements of an aircraft. The present invention is directed specifically to a pressure responsive device suitable for use with that apparatus.

In modern aircraft engines employing superchargers driven by exhaust gas it is desirable to select manually the required intake manifold pressure corresponding to the required power output of an engine, and to employ a pressure responsive control device for positioning the throttle valve and turbine waste gate to positions that give the desired manifold pressure.

As in other automatic control systems, a balance is desired between control sensitivity, which is desirable, and unstable operation or hunting, which is undesirable. It above mentioned airplane engine manifold pressure control system is more stable in its operation at the lower power requirements than at high power, and it is therefore possible to employ a more sensitive control at the lower power settings, as has been pointed out in my aforementioned application, Serial No. 659,651.

It is an object of the invention, therefore, to provide a pressure responsive device that is more sensitive to pressure changes at low values of pressure than at higher pressures.

In order to maintain desired manifold pressure at higher altitudes it is necessary to run the turbine waste gate toward closed position thereby increasing the amount of supercharging. A device responsive only to manifold pressure would accomplish this only in response to some decrease in manifold pressure. It is desirable to maintain the manifold pressure substantially constant regardless of altitude, especially at maximum or military power setting.

It is accordingly a further object of the invention to provide a pressure responsive device in which ambient pressure will shift the control point at which the primary control pressure actuates the device.

When the engine is being idled, there is no 'actual power requirement, and it is desirable that the turbine waste gate be fully open and that the throttle be moved very nearly closed regardless of manifold pressure.

has been found that the It is, therefore, a 55 further object to provide means for biasing the pressure sensitive element toward a positioncorresponding to high manifold pressure when the device is set for idling operation.

My aforementioned co-pending application, Serial No. 659,651, describes the desired relation between propeller speed and manifold pressure for normal flight conditions.

Under some flight conditions it is desirable to adjust the relation between engine speed and manifold pressure to other than the normal schedule, but it is essential that the system be restored to normal condition when entering the maximum power range.

An additional object, then, is to provide a pressure responsive device including auxiliary switching means actuated as the device is set for pressures near one extremity of its range.

Further objects will be apparent from the appended claims and from the specification and drawing, in which Figure l is a sectional elevation of a pressure responsive device incorporating various features of the invention,

Figure 2 is an elevation, partly in section, of the device of Figure 1 but showing a variable resistance actuated by the mechanism appearing in Figure I,

Figure 3 is an elevation showing the reverse side of the device of Figures 1 and 2,

Figure 4 is a fragmentary section taken substantially on line t4 of Figure 3, and

Figure 5 is a diagrammatic showing of a system employing the device illustrated in Figures 1 to 4, inclusive.

Referring now to the drawing, a pressure responsive controller ID is illustrated in Figures 1 to 4 and includes a housing II which serves to support the various elements of the device. The lower portion of the housing II is shaped to provide a chamber l2 to the lower wall of which is secured an aneroid bellows l4 having a movable wall iii. A seal-off bellows ll of somewhat smaller diameter than the bellows l4 closesan opening in the upper portion of the body H that forms the chamber l2. A member 20 that is connected to the movable wall 15 of the bellows l4 and also to the seal-off bellows ll extends through the opening in the chamber l2. The member 20 is rovided with a reduced portion 2| that cooperates with a plate 22 for limiting the extent of movement of the member 20. As seen in Figure 2, a pair of flexible reeds 24 and 25, each engaging the member 20 at one end and a portion of the housing H at the other end, serve to guide the member 25 as it is positioned vertically by the bellows i4 and I1.

A pressure connection 21 serves to transmit the control pressure to the chamber 2. It will be apparent that since the bellows I4 is of somewhat larger diameter than the bellows |1 an increase of pressure within the chamber l2 will move the bellows wall |5 downwardly and therefore the member 25 also.

The member is urged upwardly against the pressure in the chamber |2 by a spring 35 that has its upper end attached to the housing by an adjustable connection 3| that positions a screw 32 and a plug 33 which is threaded externally to engage the upper end of the spring 35. The spring 35 is arranged to urge the member upwardly directly in line with its normal movement as determined by the bellows H and I1 and by the reeds 24 and 25. Adjustment of the spring with respect to the housing changes the force due to pressure in the chamber 1 2 necessary to move the bellows and member 25 downwardly, while adjustment of the spring 35 with respect to the plug 33 changes the rate of the spring 35.

Member 25 is also urged upwardly by a pair of springs 35 and 35 that are arranged symmetrically on either side of the member 25 and pivotally attached thereto by means of a bracket 31. The upper ends of the springs 35 and 36 are secured to the outer ends of spring support levers 4 39 and 40 by means of adjusting screws 4| and 42.

The initial spring rate of the springs 35 and 36 may be adjusted to a certain extent by varying the position of the outer ends thereof on externally threaded plugs 43 and 44 that are positioned with respect to the levers 39 and 45 by the adjusting screws 4| and 42.

The inner ends of the levers 39 and 45 are pivotally carried in the housing II on a pair of shafts 45 and 46. The shafts 45 and 46 are provided with intermeshing gears 41 and 48 for causing the levers 39 and 45 to move simultaneously. It will be noted that the arrangement is such that the levers 39 and 45 will be swung toward the vertical at the same time. The shaft 45 is provided with an adjusting lever located outside the housing II as shown in Figures 3 and 4. A roller 5| pivoted in the lever 55 adapts the device for control by cam means 53 as will be pointed out hereinafter.

The effective spring rate of the control device at any particular setting of the levers 39 and 45 and therefore the sensitivity, will depend on the spring rates of the spring 35, springs 35 and 35 and also on the spring rates of the bellows i4 and H. The overall effective spring rate of the device may be adjusted, for any particular position of the levers 39 and 45, by positioning the plug 33 with respect to the spring 35 and by positioning the plugs 43 and 44 with respect to the springs 35 and 36.

It will be apparent that the springs 35 and 36 exert their greatest force tending to reduce the size of the chamber l2 when the levers 39 and 45 are swung to a vertical position paralleling the fixedv spring 30. As the levers 39 and 49 are swung away from the vertical position, the component of the force of the springs 35 and 36 acting vertically on the member 20 is reduced. It will be noted that the springs 35 and 36 are, in effect, pivoted at their lower ends substantially in line with the pivotal axes of the levers 39 and 40. For this reason, little or no force is required to position the levers 39 and 40, the change in 4 force urging the member 25 upwardly being obtained by changing the effective component of the springs 35 and 35 in that direction.

It will be noted also that the springs 35 and 36 will have their greatest spring rate when they are adjusted to the vertical position. As they are swung away from the vertical their effective spring rate will diminish. In other words, when the springs 35 and 38 are swung outwardly, a relatively smaller force will be required to move the member 25 through a predetermined distance than when they are in a more nearly vertical position.

As seen in Figure 1, the member 25 is provided with a leaf spring 55 that extends upwardly at an angle beneath the springs 35 and 35. When the levers 39 and 45 are swung outwardly to a point near their extremity of motion, the springs 35 and 35 will engage the leaf spring 55 or the spring 55 may engage the ends of the levers 39 and 45 with the result that the member 25 will be biased downwardly with the same eil'ect on the member 25 as though the pressure in the chamber l2 had increased. Adjustment of the levers 39 and 45 after engagement of the leaf spring 55 will therefore provide a varying degree of downward bias on the member 25. Obviously, the spring 55 could directly engage the levers 35 and 45 rather than the springs 35 and 35.

A rack 58 is pivoted in the member 25 and cooperates with a pinion 55 as indicated in dotted lines in Figure 2 that is rotatable with respect to a plate 62 that is, in turn, suitably supported in the housing A roller 53 also pivoted in the plate 52 serves to keep the rack 58 in engagement with the pinion 55. The pinion 55 serves to position an arm 55 that engages and wipes over an electrical resistance 55. The arm 55 is provided with an electrical insulating portion 51 to isolate it electrically from the remainder of the device. Likewise, the electrical resistance 55 is mounted on an insulating plate 59 that is suitably secured to the plate 52.

Referring again to Figures 3 and 4, it will be seen that the adjusting lever 55 is provided with a pair of stops 12 and 13 that cooperate with a projection 14 on the housing The stop 12 is provided to limit adjustment in calling for maximum pressure and the stop 13 limits movement in the direction calling for minimum pressure.

The adjusting lever 55 is also provided with an arcuate slot 16 in which is adjustably mounted The cam 18 engages a plunger 18 for actuatin a single pole double throw snap switch that is mounted inside the housing ll upon a bracket 8|. The snap switch 85 may be of any suitable type which are well known and it is not thought necessary to describe the details thereof It will be noted that by suitably adjustin the cam 18 in the slot 1-5 the switch 85 may be actuated at any desired position of the adjusting lever 55.

The roller 5| on the adjusting lever 55 may be positioned by a suitable cam 53 which has been illustrated as of the type employed in my copending application Serial No. 659,651, filed on even date herewith.

The operation of the device will be described in connection with the diagrammatic control system illustrated in Figure 5. The pressure responsive device I5 is here shown in a system for controlling the intake manifold pressure of an aircraft engine. The chamber H of the device is connected by means of the pressure connection 21 to the intake manifold 09 of an internal comiustion aircraft engine I00. The engine I lirectly drives a propeller I02 and a direct driven Jlower I03 withinthe induction system. Exaaust from the engine I00 passing through an exhaust pipe I04 also drives a turbine I05 which rotates a second supercharger I06. The super- :harger I06 conveys air'to a carburetor I01 that includes a throttle valve I00. The amount of supercharging accomplished by the supercharger I06 depends on the position of a waste gate valve I09 located in the exhaust system beyond the turbine I05. The pressure within the intake manifold 99 will increase as the throttle valve I06 is opened and will be further increased as the waste gate valve I09 is moved toward closed position to force more exhaust gas through the turbine I05 and increase the speed of rotation of the supercharger I06.

A reversible electric motor II2 positions the 1 throttle valve I08 and a reversible electric motor II4 positions the waste gate valve I09. A suitable electrical network and electronic amplifier II6 of the type described in my co-pending application Serial No. 659,651, filed on even date herewith, is supplied with power by the connection III. The amplifier H6 is connected to the motor II2 by wires IIS and to the motor II4 by wires H9. The motors H2 and H4 sequentially open the throttle valve I08 and close the waste gate valve I00 with a small amount of overlap between the movements thereof as the alternating current voltage supplied to the input terminals I and I2I of the network and amplifier H6 is changed from a relatively high value to a relatively low value.

A lever I that corresponds to the usual throttle lever is located in the pilots compartment. Adjustment of the lever I25 positions the cam 53 through a cable I26 and the cam 53 positions the roller 5| and the adjusting lever 50 thereby swinging the levers 39 and to adjust the control point of the pressure responsive device I0. The lever I25 also adjusts a propeller speed control I28 on the engine I00 through the cable I26 and a cable I23.- In the complete system described in my co-pending application Serial No. 659,651, filed on even date herewith, a more complete system for correlating the settings of the propeller speed control and the setting of the pressure responsive device is illustrated. It is sufilcient here to show that the propeller speed control and the pressure responsive device are actuated by movements of the same manual control.

The input terminal I20 of the electrical network and amplifier II6 is connected to one end of the electrical resistance 66 of the pressure responsive device I0 by a wire I3l. A transformer I33 having a primary winding I34 also includes a secondary I35, one end of which is connected to the wire I3I and the other end of which is connected to the opposite end of the electrical resistance 66 by a wire I36. The slider 65 cooperating with the resistance 66 is connected to the center pole of the switch 80 by means of a wire I38. The wire I38 is normally connected through the switch 80 to a wire I40 leading to a manually adjustable arm I42 that is positionable with respect to a resistance I43. The resistance Y I43 is connected across a secondary I45 of a transformer I46 having a primary winding I41. The midpoint of the secondary winding I45 is connected through a wire I40 to the other input terminal I2I of.the electrical network and amplifier II6.

Assuming that the arm I42 is positioned in the mid-point of the resistance I43, the voltage applied to the input terminals I20 and I2I of amplifier II6 will depend entirely upon the position of the slider 65 with respect to the electrical resistance 66 of the pressure control device I0. If it is desired to change the relation between propeller speed and intake manifold pressure, the arm I42 may be manually positioned on the resistance I43 to superimpose an alternating current voltage on the voltage as determined by the pressure control device. The alternating current supplied to the primary windings of the transformers I33 and I46 bear a definite phase relation to each other so that adjustment of the arm I42 will have the effect of either adding to or subtracting from the voltage output as determined by the potentiometer comprising resistance 66 and slider 65 of the pressure control device. Under certain conditions of flight, this adjustment for variations from normal relation between propeller speed and manifold pressure may be desirable, but under military or emergency power conditions this eiiect must be eliminated or the result will either be insuiilcient manifold pressure to correspond to the propeller speed or a dangerously high manifold pressure.

The switch serves to shunt the control afforded by the arm I42 and resistance I43 out of the system so that when the adjusting arm 50 is positioned so that the cam 16 engages the .switch 80 the wire I38 will be connected directly to the amplifier input terminal I2I through a wire I52 and the wire I43 directly to the terminal I2I, thus restoring the normal relationship between propeller speed and manifold pressure. It will be noted that the cam I8 is adjustable in the arm 50 so that normal operating conditions may be established at any desired position of the manually operated lever I25. This setting will depend upon experience with the particular type of aircraft involved.

Referring again to the pressure control device I0, it will be noted that the force opposing expansion of the chamber I2 and downward movement of the movable wall I5 is obtained by the single vertical spring 30 and by the pair of springs 35 and 36 which are simultaneously rotated to change the force component opposing the control pressure. When the springs 36 and 36 are parallel to the direction of bellows movement, the entire force of the springs will act on the bellows assembly, but as the springs are positioned through a greater angle their effective component will be reduced and the controlled pressure will be reduced due to repositioning of the throttle valve I08 and the waste gate valve I09. It will be noted that as the springs 35 and 36 are adjusted for lower control pressure the effective spring rate will also be reduced. When the spring rate is reduced, a smaller change in pressure is required to move the potentiometer slider 65 from one end of the resistance 66 to the other and therefore the device will be more sensitive. When the power plant is operating in the normal cruising or rated power range operation is somewhat more stable than in the emergency or military power range, and it is therefore possible to increase the sensitivity of the manifold pressure control when adjusted for lower manifold pressures. The pressure control device I0 may be adjusted so that at the various power require- 7 ments control will be as sensitive as possible for the stability of the power plant that exists at the power desired. The adjusting means II is regulated so that the vertical spring II will have the desired tension in conjunction with the tension of the springs 35 and It as adjusted by the screws 4| and 42 to give the desired control pressure together with the desired spring rate at the various power settings. The relation between the sensitivity of the device at the emergency or military power setting and at a particular reduced power setting may be determined by adjusting the relation between the rate of the spring 30, as determined by the setting of the spring plug 38 therein, and the rate of the springs II and It, as determined by the settings of the spring plugs 48 and H with relation to those springs.

It will be noted that the lower ends of the springs II and 86 are pivoted in the member 20 at points substantially in line with the pivot for the levers 39 and I in the housing ll. Hence, it will be seen that pivoting the levers ll and II in the housing I i results in practically no change in length of the springs ll and It and hence there is a minimum tendency for the spring to have a force of reaction through the levers 35 and 86 that will tend to position the adjusting lever 50 and cause a reactive force back to the manual control lever I25.

As previously pointed out, the leaf spring ll associated with the member 20 engages the springs I and 38 when the manual control lever III is moved to the right for placing the levers I! and 40 close to horizontal position. In this position the control device is adjusted for engine idling condition, and it is desirable that the waste gate valve I08 be opened regardless of any other condition. Engagement of the leaf spring ll by the springs 35 and 38 will have the same eflect on the member 20 as increased manifold pressure, and the slider 85 will be moved to a position with respect to the resistance 66 in which the waste gate valve ill! will be opened and the throttle valve I" will be moved towards closed position. However, since the spring 55 is resilient, it will be possible to vary manually the position of the throttle valve I08 suillciently to maintain engine operation.

The arrangement of the aneroid bellows H and the seal-oil bellows i1 is such that increased altitude causes a response of the member 20 in the same direction as a decrease in manifold pressure. As a result, the device will call for slightly higher manifold pressure at higher altitudes. However, at increased altitudes the waste gate must be moved towards closed position in order to maintain desired manifold pressure. To do this, the slider 65 must be repositioned with respect to the resistance 86, and this can be done only by lowering the effective pressure in the chamber H to a value that will position the slider 65 on the resistance 66 to a position that will give the desired position of the waste gate valve I". The eil'ective diameter of the bellows i1 is chosen with respect to the effective diameter of the bellows It to compensate for this droop" of the control system. Such compensation is most important at the maximum power setting. Since it is not possible to adjust the power setting beyond the maximum setting to compensate for droop in the system due to increased altitude, the bellows l1 and I have been selected to be of the proper eflective diameters to eliminate the system droop at the maximum power setting.

While the pressure control device has been illustrated as or a type to be used to control the 8 manifold pressure of an aircraft engine, it will be understood that it could be used equally well on other applications. For example, it would be possible to use the device described in any application where it is desired to control pressure, for example, steam pressure or water pressure. While the control means has been illustrated as a variable electrical resistance, it will be apparent that a simple switching means could be substituted therefor. Likewise, the control means actuated by the member It could be a valve for varying the flow or a fluid.

I claim as my invention: 7

1. In a pressure responsive device, in combination, an expansible chamber, a member movable by said chamber, control means actuated by said member; a spring opposing expansion of said chamber, a lever having a fixed pivot and being operatively connected to said spring to change the component of force of said spring opposing expansion of said chamber while maintaining the actual force of said spring substantially constant, and means for pivotally adjusting said lever.

2. In a pressure responsive device, in combination, an expansible chamber, a member movable by said chamber, control means actuated by said member, a first spring having a fixed support acting on said member, a second spring opposing expansion of said chamber, a lever having a fixed pivot and being operatively connected to said second spring to change the component of force of said second spring opposing expansion or said chamber while maintaining the actual force of said spring substantially constant and means for pivotally adjusting said lever.

3. In a pressure responsive device, in combination, an expansible chamber, a member movable by said chamber, control means actuated by said member, a first spring having a fixed support actingon said member, a second spring opposing expansion of said chamber, a lever having a fixed pivot and being operatively connected to said sec- I 0nd spring to change the component 01' force oi said second spring oppos sexpansion of said chamber while maintaining the actual force of said spring substantially constant, means for pivotally adjusting said lever, means for adjusting the force of said first spring, and means for adjusting the position of said second spring with respect to said lever.

4. In a pressure responsive device, in combination, a support, an expansible chamber carried by said support, a member movable by said chamber in a predetermined path, control means actuated by said member, a spring carried by said support for directly opposing expansion of said chamber. a second spring carried by said support and acting on said member, and means for changing the angle of the application of the force of said second spring with respect to the direction of movement of said member while maintaining the actual force of said spring substantially constant.

- 5. In a pressure responsive device, in combination, a support, an expansible chamber carried by said support, a member translatable by said chamber, control means actuated by said member, a pair of springs symmetrically located with respect to said member, one portion of each of said springs being connected to said member, and another portion of each of said springs being pivotally mounted in said support for varying symmetrically the spring component opposing expansion of said chamber while maintaining the aseasas actual force of said springs substantially constant.

6. In a pressure responsive device, in combination, an expansible chamber, a member movable by said chamber, control means actuated by said member, a first spring having a predetermined spring rate acting on said member, a second spring acting on said member, means for varying the effective spring rate of said second spring while maintaining the actual force of said second spring substantially constant, and means for adjusting the forc of said first spring applied to said member.

'1. In a pressure responsive device, in combination, a support, an expansible chamber carried by said support, a member translatable by said chamber, a pair of springs symmetrically disposed, with respect to said member and acting on said member, levers pivoted in said support on axes substantially in line with the connections of said springs to said member and normal to the movement of said member, said levers being operatively connected to said springs, means interconnecting said levers for causing simultaneous pivoting thereof while maintaining their symmetry with and means for adjusting said levers pivotally.

8. In a pressure responsive device, in combination, a support, an expansible chamber carried by said support, a member translatable by said chamber, a resistor carried by said support, means actuated by effective value of said resistor, springs on opposite sides of said member and conjointly acting on said member to oppose said chamber, levers pivoted in said support on axes substantially in line with the connections of said springs to said member, said levers being operatively connected to said springs, means interconnecting said levers for causing simultaneous pivoting thereof, and means for adjusting said levers pivotally.

9. In a control device, in combination, a condition responsive elemen a control element positioned by movement of said condition responsive element, a spring having one portion acting on said condition responsive element and another portion connected to an adjustable abutment, said abutment being movable through a predetermined range for varying the force of said spring that acts on said condition responsive element, and a separate connection between said abutment and said condition responsive element eflective only in a predetermined portion of the adjustable range of said abutment.

10. In a pressure responsive device, in combination, an expansible chamber having a first movable wall comprising an aneroid bellows, and having a second movable wall opposing said first wall and comprising a bellows of smaller diameter than said aneroid bellows subjected on its opposite side to ambient pressure, a member interconnecting said first and second movable walls and extending out of said chamber, control means actuated by said member, a spring opposing expansion of said chamber, a lever having a fixed pivot and being operatively connected to said spring to change the component of force of said spring opposing expansion of said chamber while maintaining the actual force of said spring substantially constant, and means for pivotally ad- Justin: said lever.

respect to said member, I

said member for varying the- 11. In a pressure responsive device, in combination, a support, an expansible chamber carried by said support, a member movable by said chamber, control means actuated by said member, a spring acting on said member and opposing expansion of said chamber, a lever pivoted in said support and operatively connected to said spring to vary the component of the force of said spring eifective to position said member, switching means carried by said support, a cam movable with said lever to actuat said switching means, means for angularly adjusting said cam in said lever about termine the position of said lever at which said switch is actuated, and means for pivotally adjusting said lever.

12. In a pressure responsive device, in combination, a support, an expansible chamber carried by said support, a member movable by said chamber, control means actuated by said member, a spring acting on said member and opposing expansion of said chamber, a lever pivoted in said support for varying the force of said spring on said member, switching means carried by said support, cam means for actuating said switching means, said cam means being carried by said lever and adjustable with respect thereto for varying the setting of said lever at which said switching means is actuated.

13. A device for applying an adjustable force to oppose a pressure responsive element comprising, a first spring adapted to act directly on the element, a second spring, and a lever operatively connected to said second spring and rotatable about an axis for changing th component of force of said second spring acting on the element while maintaining the actual force of said second spring substantially constant.

14. In a control device, in combination, a condition responsive element, a control element positioned by movement of said condition respon- SiVe element, a spring having one portion acting on said condition responsive element and another portion connected to an adjustable abutment, said abutment being movable through a predetermined range for varying the force oi said spring that acts on said condition responsive element, and a second spring adapted to interconnect said abutment and said condition responsive element only when said abutment is located within a predetermined fractional portion of its adjustabie range.

STEPHEN CRUM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 39,114 Breroor Juiy 'l, 1863 999,329 Mehring Aug. 1, 1911 1,344,340 Fulton June 22, 1920 2,170 .744 Adler Aug. 22, 1939 2,182,123 Grisdale Dec. 5, 1989 2,203,523 Cunningham June 4, 1940 2,256,473 De Giers Sept. 23, 1941 2,283,378 Liner May 19, 1942 2,356,202 Benjamin Aug. 22, 1944 the axis of said lever to de- 

